There has hitherto existed a steering apparatus equipped with a steering lock mechanism that restricts a rotation of a steering wheel in order to prevent the vehicle etc from being stolen. The steering lock mechanism is configured to include a key lock collar fitted on a steering shaft and a steering lock device fitted to a column provided on an external side thereof, in which a lock bar provided on the steering lock apparatus is fitted into a grove or the like formed in the key lock collar, thereby disabling the steering wheel from being steered when the vehicle is to be stolen by restricting a rotation of the shaft.
In a conventional steering lock mechanism, it happened that if the steering wheel is rotated by strong force in a steering locked state, the steering lock mechanism was broken, and a lock function was damaged.
Such being the case, there exists a steering lock mechanism configured to rotate the key lock collar about the steering shaft when a predetermined or larger degree of force is applied so as to prevent a breakage, and to give a proper friction to such an extent as to disable the steering wheel from being steered, thereby preventing the vehicle from being stolen.
This type of steering lock mechanism is requested to be compatible with both of stabilizing a slip characteristic between an outer peripheral surface of the steering shaft and an inner peripheral surface of the key lock collar and setting a slip load to such a degree that the steering lock mechanism is not broken. Hence, there is a configuration for acquiring a predetermined magnitude of stable slip torque (frictional force) by forming a non-contact portion between the outer peripheral surface of the steering shaft and the inner peripheral surface of the key lock collar (refer to, e.g., Japanese Patent Application Laid-Open Publication No. 2010-163115).
Further, there is a configuration contrived not to cause an excessive frictional resistance by machining a grease groove in the steering shaft, retaining grease in this grease groove and supplying the grease to a frictional surface between the key lock collar and the steering shaft (refer to, e.g., Japanese Patent Application Laid-Open Publication No. H07-291095).
Moreover, there is a configuration for the purpose of protecting the steering lock mechanism, in which a slip ring is attached to a fitting portion between the key lock collar and the steering shaft (refer to, e.g., Japanese Patent Application Laid-Open Publication No. 2005-351457).